NEW 45 engine

Help Support intlwaters.com:

ALLAN YUEN

Well-Known Member
Joined
Jan 14, 2005
Messages
6,078
I like the 91 M1 motor
I ran a pair in a twin at Brandon this year
Out of the box the performance was quite good.

There is 91 M1 and 91 Inline. The 91 inline appears to have the M1 features
Best CMB 91 M-line red head 6 bolts than CMB RS EVO gold head four bolts? Is M-line more powerful? And use turbo plug Rossi 8T plug?
 

AgafonovRoman

Well-Known Member
Joined
Nov 27, 2014
Messages
377
I don't like it. But using a square drive remedies the situation (by allowing the flex shaft to "float" within the coupler, and not push up against the crankshaft, transferring the torque to the rear rotor assy)
I think when you use a cone on a flywheel and tight it with any regular nut(square ore coupler) it stops what move... 🤔
 

dr gary turner

Well-Known Member
Joined
Dec 25, 2004
Messages
2,420
I have not seen an M1 P/S for 45

My M1 21 the difference is a dish piston and turbo head button
It actually came with 2 HB , one for low nitro and one for high nitro
 

Rudi Arnesen

Well-Known Member
Joined
Nov 5, 2003
Messages
513
I talked Tony Australia about 91 m-line it can use both collet and square. Not arrive new CMB45 M-line yet because factory workers delay from Covid-19
You cannot use rund flex on M-line engines, they are not designed for it only square drive
 

Rudi Arnesen

Well-Known Member
Joined
Nov 5, 2003
Messages
513
If you dismantle the engine you will see why. All the energy will be on the front end bearing and to the front part of the crank
 

gilbert galli

Well-Known Member
Joined
Apr 27, 2013
Messages
62
on engines which do not have a front bearing retaining circlip and if the drive dog play is too important, it is the bearing which takes the thrust of the propeller and this forces on the crankshaft, with a square drive with ferule the pushed is done on the strut
 

Ian Inverarity

Well-Known Member
Joined
Nov 2, 2002
Messages
2,661
Gilbert, a Zenoah (for example) also does not have a circlip to retain the bearing at the collet end, also does not fasten the crankshaft to the inner race of the bearing at the collet end, also has the prop thrust taken through the crankshaft and is resisted by the bearing at the opposite end from the collet. By far the majority of Zenoahs would run that way without issues. Why would this be a problem for the CMB M line engines which in fact support the crankshaft better with 2 bearings at the collet end which should prevent deflection of the crank pin and collet end of the crankshaft under load?
 

gilbert galli

Well-Known Member
Joined
Apr 27, 2013
Messages
62
it is possible that the bearings are mounted tighter in a zenoah crankcase, the longitudinal play of a zenoah crankshaft may be greater,
the connecting rod of a zenoah is also freer
 

Ian Inverarity

Well-Known Member
Joined
Nov 2, 2002
Messages
2,661
Gilbert;
1. No, from my experience about the same.
2. Not dissimilar, but how is that relevant anyway? If the Zenoah had excessive axial play then potentially the crank could run on the side of the conrod and I’ve never seen that issue.
3. You mean axially? Zenoah rods are tighter at the piston end of the conrod compared to CMB nitro engines.
What damage or harm do you expect to an M line engine and what would cause it?
 

gilbert galli

Well-Known Member
Joined
Apr 27, 2013
Messages
62
it is possible that the thrust on the crankshaft with a faster engine speed causes clamping or breakage,
it should be remembered that the imbra races last longer in the fsro or fsrv category
 
Last edited:

Ian Inverarity

Well-Known Member
Joined
Nov 2, 2002
Messages
2,661
Gilbert, so are you saying the crank shaft web may slip on the crank pin trapping the conrod between the two crank webs? Have you seen this with the M Line engines? How is this RPM related? We will watch out for this issue! What I can say is that I have has several RS101 crank pins break from high RPM use while only supported by two bearings and using square drive. I made my own 2 bearing housing for my RS101 Evo before CMB released the DFB and M line engines to stop the pin breakage.
 

Joe Warren

Well-Known Member
Joined
Nov 29, 2003
Messages
7,920
the M91 Piston is a mild mod on front of liner to improve fuel flow. something most were doing 10 years ago.
 

LohringMiller

Well-Known Member
Joined
Jan 25, 2017
Messages
664
I have no experience with the nitro CMBs, but Mike Bontoft built a new front end that added another bearing to the front of the CMB 35. This reduced crankshaft flexing that caused flywheel strikes on the magneto. We also replaced the magneto with the Quickdraw solid state ignition.

Lohring Miller


Ignition comparison side.JPG
 

Latest posts

Top